Highly selective acylation of polyamines and aminoglycosides by 5-acyl-5-phenyl-1,5-dihydro-4H-pyrazol-4-ones

A highly selective acylating reagent with remarkable recognition of primary amines in monoacylation of polyamines and aminoglycosides.


Experimental Procedure for the Kinetic Study of the Reaction Between BCPP and Amines
Rate constants for the reaction of BCPP with a series of amines were determined using UV-Vis spectroscopy at 24±0.5 o C in dichloromethane. BCPP (1a) has an absorbance in the range 300 − 440 nm (covers visible light range), while other reactants and products absorb only in UV range. It allows monitoring the disappearance of BCPP at a certain wavelength (e.g. 380 nm). All kinetic measurements have been carried out above DCM cutoff (λ = 245 nm).
Absorbance for a series of solutions of BCPP in DCM was measured at 24 °C. Extinction coefficient ε was determined from Beer-Lambert law: A = εcl (l = 1 cm) as slope of the linear plot A = f(c). Extinction coefficient ε = 2920±70 was determined from three parallel experiments.
Determination of second order reaction rate.
Kinetic runs were performed for the reaction of BCPP with a series of amine solutions of different concentrations (C amine ≥ 10•C BCPP ).
Considering that the extinction coefficient for BCPP at 380 nm ε = 2920, a BCPP solution was prepared to have an absorbance A = 0.4−0.8 (at 380 nm). Concentrations of amine solutions (C amine ≥ 10•C BCPP ) were used to have reaction times less than one hour. mm, was mounted, using Paratone oil, onto a nylon loop. The data were collected at 98(2) K using a Rigaku AFC12 / Saturn 724 CCD fitted with MoKα radiation (λ = 0.71075 Å). Data collection and unit cell refinement were performed using CrystalClear software. 10 The total number of data were measured in the range 6.46° < 2θ < 50.1° using ω scans. Data processing and absorption correction, giving minimum and maximum transmission factors (0.546, 1.000), were accomplished with CrystalClear 10 and ABSCOR 11 , respectively. The structure, using

S38
Olex2 12 , was solved with the ShelXT 13 structure solution program using direct methods and refined (on F 2 ) with the ShelXL 14 refinement package using full-matrix, least-squares techniques. All non-hydrogen atoms were refined with anisotropic displacement parameters.
Electron density peaks were used to determine the hydrogen atoms bound to N2, C5, C6 and C7 atoms. All other hydrogen atom positions were determined by geometry and refined by a riding model.